The immediate background art is that documented in German Patent Document DE 42 27 106, which discloses a combination instrument unit for motor vehicles. This instrument can be switched between two display sections at the user's discretion. One of these display sections exhibits the features of display instruments as presented, for instance German Patent Document DE-PS 38 03 190 or DE-OS 37 36 761. The other display section is a digital information display which is generated outside the display area and fed into said display area by means of a projection technique.
A drawback of this instrument is that the display sections can only be selected alternatively. When the digital information display is projected into the display area, the gauges located behind the transparent cover can no longer be read. In view of their size, moreover, all of the instruments referred to are suitable only for installation in instrument panels of conventional dimensions, i.e. offering a comparatively large amount of space.
Especially in the design of compact vehicles, given the limited display area of their instrument panels, it is a problem that despite such space constraints, the arc-shaped gauges must retain easy readability, while the same display area should also show such comprehensive additional information as has already become a standard feature on larger vehicles, so that the users of second `city` cars need not miss out upon this additional information.
One conceivable way of addressing this problem would be to arrange the fixed and variable symbol cells for the symbolic information display inside the circular area of the analog gauges. In this case, however, the pointer movement over the analog dial would interfere with the readability of the symbols, which are necessarily small. In addition, the driver would find it more difficult to maintain an overview of the information supplied if the symbols were distributed over the entire surface of the display area. The same holds true if the symbols are distributed in the area between two adjoining round dials.